US7874820B2 - Compressor unloading valve - Google Patents

Compressor unloading valve Download PDF

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Publication number
US7874820B2
US7874820B2 US11/719,617 US71961705A US7874820B2 US 7874820 B2 US7874820 B2 US 7874820B2 US 71961705 A US71961705 A US 71961705A US 7874820 B2 US7874820 B2 US 7874820B2
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United States
Prior art keywords
condition
valve element
spring
compressor
displacement volume
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related, expires
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US11/719,617
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English (en)
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US20090148332A1 (en
Inventor
Stephen L. Shoulders
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Carrier Corp
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Carrier Corp
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Assigned to CARRIER CORPORATION reassignment CARRIER CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: SHOULDERS, STEPHEN L.
Publication of US20090148332A1 publication Critical patent/US20090148332A1/en
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Expired - Fee Related legal-status Critical Current
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
    • F04C18/08—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
    • F04C18/12—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type
    • F04C18/14—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons
    • F04C18/16—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons with helical teeth, e.g. chevron-shaped, screw type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
    • F04C28/10—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids characterised by changing the positions of the inlet or outlet openings with respect to the working chamber
    • F04C28/12—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids characterised by changing the positions of the inlet or outlet openings with respect to the working chamber using sliding valves
    • F04C28/125—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids characterised by changing the positions of the inlet or outlet openings with respect to the working chamber using sliding valves with sliding valves controlled by the use of fluid other than the working fluid
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
    • F04C29/12—Arrangements for admission or discharge of the working fluid, e.g. constructional features of the inlet or outlet
    • F04C29/124—Arrangements for admission or discharge of the working fluid, e.g. constructional features of the inlet or outlet with inlet and outlet valves specially adapted for rotary or oscillating piston pumps
    • F04C29/126—Arrangements for admission or discharge of the working fluid, e.g. constructional features of the inlet or outlet with inlet and outlet valves specially adapted for rotary or oscillating piston pumps of the non-return type
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/7722—Line condition change responsive valves
    • Y10T137/7771—Bi-directional flow valves
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/7722—Line condition change responsive valves
    • Y10T137/7771—Bi-directional flow valves
    • Y10T137/7772—One head and seat carried by head of another
    • Y10T137/7777—Both valves spring biased
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49716—Converting

Definitions

  • the invention relates to compressors. More particularly, the invention relates to refrigerant compressors.
  • Screw-type compressors are commonly used in air conditioning and refrigeration applications.
  • intermeshed male and female lobed rotors or screws are rotated about their axes to pump the working fluid (refrigerant) from a low pressure inlet end to a high pressure outlet end.
  • sequential lobes of the male rotor serve as pistons driving refrigerant downstream and compressing it within the space between an adjacent pair of female rotor lobes and the housing.
  • sequential lobes of the female rotor produce compression of refrigerant within a space between an adjacent pair of male rotor lobes and the housing.
  • the interlobe spaces of the male and female rotors in which compression occurs form compression pockets (alternatively described as male and female portions of a common compression pocket joined at a mesh zone).
  • the male rotor is coaxial with an electric driving motor and is supported by bearings on inlet and outlet sides of its lobed working portion. There may be multiple female rotors engaged to a given male rotor or vice versa.
  • the refrigerant When one of the interlobe spaces is exposed to an inlet port, the refrigerant enters the space essentially at suction pressure. As the rotors continue to rotate, at some point during the rotation the space is no longer in communication with the inlet port and the flow of refrigerant to the space is cut off. After the inlet port is closed, the refrigerant is compressed as the rotors continue to rotate. At some point during the rotation, each space intersects the associated outlet port and the closed compression process terminates.
  • the inlet port and the outlet port may each be radial, axial, or a hybrid combination of an axial port and a radial port.
  • Such unloading is often provided by a slide valve having a valve element with one or more portions whose positions (as the valve is translated) control the respective suction side closing and discharge side opening of the compression pockets.
  • the primary effect of an unloading shift of the slide valve is to reduce the initial trapped suction volume (and hence compressor capacity); a reduction in volume index is a typical side effect.
  • Exemplary slide valves are disclosed in U.S. Patent Application Publication No. 20040109782 A1 and U.S. Pat. Nos. 4,249,866 and 6,302,668.
  • the desired degree to which a compressor may be unloaded is often application-specific. High degrees of unloading (e.g., down to an exemplary 15% of full load capacity) may be preferred for some applications.
  • a compressor has housing having first and second ports along a flow path. One or more working elements cooperate with the housing to define a compression path between suction and discharge locations along the flow path.
  • An unloading valve has a valve element having a range between a first condition and a second condition, the second condition being unloaded relative to the first condition. Means bias the valve element toward a third condition intermediate the first and second conditions.
  • the means may comprise a first and second springs.
  • the springs may be on opposite sides of a piston engaged to the valve element.
  • the means may be introduced in a reengineering of an existing compressor configuration and/or a remanufacturing of an existing compressor.
  • the reengineering may be an iterative process performed on hardware or as a simulation/calculation.
  • the reengineering or remanufacturing may comprise adding a second spring to act against an existing first spring of the baseline compressor.
  • FIG. 1 is a longitudinal sectional view of a compressor.
  • FIG. 2 is a transverse sectional view of a discharge plenum of the compressor of FIG. 1 , taken along line 2 - 2 .
  • FIG. 3 is a sectional view of a slide valve assembly of the discharge plenum of FIG. 2 in a fully loaded condition, taken along line 3 - 3 .
  • FIG. 4 is a view of the slide valve of FIG. 3 in a relatively unloaded condition.
  • FIG. 5 is a view of the slide valve of FIG. 3 in a neutral condition more loaded than the FIG. 4 condition and less loaded than the FIG. 3 condition.
  • FIG. 1 shows a compressor 20 having a housing assembly 22 containing a motor 24 driving rotors 26 and 28 having respective central longitudinal axes 500 and 502 .
  • the rotor 26 has a male lobed body or working portion 30 extending between a first end 31 and a second end 32 .
  • the working portion 30 is enmeshed with a female lobed body or working portion 34 of the female rotor 28 .
  • the working portion 34 has a first end 35 and a second end 36 .
  • Each rotor includes shaft portions (e.g., stubs 39 , 40 , 41 , and 42 unitarily formed with the associated working portion) extending from the first and second ends of the associated working portion.
  • Each of these shaft stubs is mounted to the housing by one or more bearing assemblies 44 for rotation about the associated rotor axis.
  • the motor is an electric motor having a rotor and a stator.
  • One of the shaft stubs of one of the rotors 26 and 28 may be coupled to the motor's rotor so as to permit the motor to drive that rotor about its axis.
  • the rotor drives the other rotor in an opposite second direction.
  • the exemplary housing assembly 22 includes a rotor housing 48 having an upstream/inlet end face 49 approximately midway along the motor length and a downstream/discharge end face 50 essentially coplanar with the rotor body ends 32 and 36 . Many other configurations are possible.
  • the exemplary housing assembly 22 further comprises a motor/inlet housing 52 having a compressor inlet/suction port 53 at an upstream end and having a downstream face 54 mounted to the rotor housing downstream face (e.g., by bolts through both housing pieces).
  • the assembly 22 further includes an outlet/discharge housing 56 having an upstream face 57 mounted to the rotor housing downstream face and having an outlet/discharge port 58 .
  • the exemplary rotor housing, motor/inlet housing, and outlet housing 56 may each be formed as castings subject to further finish machining.
  • surfaces of the housing assembly 22 combine with the enmeshed rotor bodies 30 and 34 to define inlet and outlet ports to compression pockets compressing and driving a refrigerant flow 504 from a suction (inlet) plenum 60 to a discharge (outlet) plenum 62 ( FIG. 2 ).
  • a series of pairs of male and female compression pockets are formed by the housing assembly 22 , male rotor body 30 and female rotor body 34 .
  • Each compression pocket is bounded by external surfaces of enmeshed rotors, by portions of cylindrical surfaces of male and female rotor bore surfaces in the rotor case and continuations thereof along a slide valve, and portions of face 57 .
  • FIG. 2 shows further details of the exemplary flowpath at the outlet/discharge port 58 .
  • a check valve 70 is provided having a valve element 72 mounted within a boss portion 74 of the outlet housing 56 .
  • the exemplary valve element 72 is a front sealing poppet having a stem/shaft 76 unitarily formed with and extending downstream from a head 78 along a valve axis 520 .
  • the head has a back/underside surface 80 engaging an upstream end of a compression bias spring 82 (e.g., a metallic coil). The downstream end of the spring engages an upstream-facing shoulder 84 of a bushing/guide 86 .
  • a compression bias spring 82 e.g., a metallic coil
  • the bushing/guide 86 may be unitarily formed with or mounted relative to the housing and has a central bore 88 slidingly accommodating the stem for reciprocal movement between an open condition (not shown) and a closed condition of FIG. 2 .
  • the spring 82 biases the element 72 upstream toward the closed condition.
  • an annular peripheral seating portion 90 of the head upstream surface seats against an annular seat 92 at a downstream end of a port 94 from the discharge plenum.
  • the compressor has a slide valve 100 having a valve element 102 .
  • the valve element 102 has a portion 104 along the mesh zone between the rotors (i.e., along the high pressure cusp).
  • the exemplary valve element has a first portion 106 ( FIG. 3 ) at the discharge plenum and a second portion 108 at the suction plenum.
  • the valve element is shiftable to control compressor capacity to provide unloading.
  • the exemplary valve is shifted via linear translation parallel to the rotor axes.
  • FIG. 3 shows the valve element at an upstream-most position in its range of motion In this position, the compression pockets close relatively upstream and capacity is a relative maximum (e.g., at least 90% of a maximum displacement volume for the rotors, and often about 99%).
  • FIG. 4 shows the valve element shifted to a downstream-most position. Capacity is reduced in this unloaded condition (e.g., to a displacement volume typically less than 40% of the FIG. 3 displacement volume or the maximum displacement volume, and often less than 30%).
  • shifts between the two positions are driven by a combination of spring force and fluid pressure.
  • a main spring 120 biases the valve element from the loaded to the unloaded positions.
  • the spring 120 is a metal coil spring surrounding a shaft 122 coupling the valve element to a piston 124 .
  • the piston is mounted within a bore (interior) 126 of a cylinder 128 formed in a slide case element 130 attached to the outlet case.
  • the shaft passes through an aperture 132 in the outlet case.
  • the spring is compressed between an underside 134 of the piston and the outlet case.
  • a proximal portion 136 of the cylinder interior is in pressure-balancing fluid communication with the discharge plenum via clearance between the aperture and shaft.
  • a headspace 138 is coupled via electronically-controlled solenoid valves 140 and 142 (shown schematically) to a high pressure fluid source 144 at or near discharge conditions (e.g., to an oil separator).
  • a port 146 is schematically shown in the cylinder at the headspace at the end of a conduit network connecting the valves 140 and 142 .
  • the portions of the conduit network may be formed within the castings of the housing components.
  • the exemplary main spring 120 acts with a force that is relatively insignificant in comparison to the net force which may developed by fluid pressures. During periods of non-operation, when fluid pressures are balanced, the main spring 120 acts as is described below.
  • the loaded position/condition of FIG. 3 can be achieved by coupling the headspace 138 to the source 144 and isolating it from drain/sink 150 by appropriate control of valves 140 and 142 .
  • the unloaded position/condition of FIG. 4 can be achieved by coupling the headspace 138 to the drain/sink 150 and isolating it from source 144 by appropriate control of valves 140 and 142 .
  • Intermediate (partly loaded) positions, not shown, can be achieved by alternating connection of headspace 138 to either the source 144 or the drain/sink 150 using appropriately chosen spans of time for connection to each, possibly in combination with isolating the headspace 138 from both source 144 and drain/sink 150 for an appropriately chosen span of time (e.g., via appropriate modulation techniques).
  • the unloaded position/condition of FIG. 4 be such that during operation the refrigerant mass flow through the compressor is as low as an exemplary 15% of the mass flow achieved when the slide valve is in the loaded position/condition of FIG. 3 .
  • the displacement volume of the position of FIG. 4 would be an exemplary 15-20% of the displacement volume of the position of FIG. 3 .
  • the displacement volume slightly above 15% would achieve the 15% flow rate due to internal leakage.
  • low rates of refrigerant mass flow may result in discharge pressure may not rising in a relatively short period of time.
  • Many systems depend on discharge pressure in source 144 to deliver oil for actuating slide valve 100 as previously described and for lubricating rotors and bearings.
  • valve position at start-up be more loaded than the unloaded position of FIG. 4 .
  • the start-up position would correspond to a mass flow rate that is in the range of 25-35% of that of the loaded position of FIG. 3 .
  • a displacement volume might be 25-50% that of FIG. 3 .
  • An exemplary means includes a spring 160 .
  • An exemplary spring 160 is a compression coil spring within the headspace 138 .
  • the exemplary spring 160 extends from a proximal end portion 162 to a distal end portion 164 .
  • the proximal end portion 162 is engaged to a boss 166 of the valve case 130 in the headspace to securely retain the spring 160 .
  • the exemplary spring 160 has dimensions and a spring constant such that the distal end 164 engages the face 168 of the piston 124 in the FIG. 4 unloaded condition but disengages at some point in the range of travel to the FIG. 3 loaded condition.
  • the spring 160 may come into play, for example, during a shutdown condition.
  • a shutdown condition pressures may equalize in the suction plenum 60 , discharge plenum 62 , cylinder interior proximal portion 136 , and headspace 138 .
  • the spring 160 will act to shift the valve element slightly away from the FIG. 4 unloaded condition (e.g., to an intermediate condition of FIG. 5 ).
  • spring 160 acts on piston 124 in opposition to spring 120 , moving piston 124 and attached slide valve 100 to the position of FIG. 5 which is slightly more loaded than that of FIG. 4 .
  • the length and spring constant of spring 160 are chosen, possibly in combination with those of spring 120 , so that the resulting position shown in FIG. 5 corresponds to a displacement volume that results in discharge pressure rising rapidly enough to ensure quick delivery of lubricant to the compressor.
  • the displacement volume corresponding to the position of FIG. 5 would typically be in the range of 25-35% of that of the loaded position of FIG. 3 .
  • the unloaded position of FIG. 4 can automatically be achieved because the action of pressures acting on faces 168 and 134 of piston 124 and on sides 106 and 108 of slide valve 100 generates sufficient force to overcome the force provided by spring 160 .
  • the unloaded position of FIG. 4 can be prevented by coupling headspace 138 to source 144 as previously described as adequate pressure in source 144 has now been developed to allow delivery of fluid to headspace 138 .
  • the spring 160 may be added in a reengineering or remanufacturing from a baseline compressor or configuration thereof.
  • the main spring 160 could have sufficient length so that start-up would be in the fully unloaded condition.
  • the main spring 160 may be preserved or modified in the reengineering or remanufacturing. One modification would be to shorten it.
  • a headspace compression spring 160 would be to have the main spring 120 be neutral at the FIG. 5 valve condition and go into tension between the FIG. 4 and FIG. 5 valve conditions.
  • the spring 160 could be another form of spring (e.g., a Belleville washer spring).
  • the spring 160 could be attached to piston 124 rather than to boss 166 of valve case 130 .

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Applications Or Details Of Rotary Compressors (AREA)
  • Compressor (AREA)
US11/719,617 2005-02-24 2005-02-24 Compressor unloading valve Expired - Fee Related US7874820B2 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2005/006307 WO2006091200A1 (en) 2005-02-24 2005-02-24 Compressor unloading valve

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US20090148332A1 US20090148332A1 (en) 2009-06-11
US7874820B2 true US7874820B2 (en) 2011-01-25

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ID=36927727

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US11/719,617 Expired - Fee Related US7874820B2 (en) 2005-02-24 2005-02-24 Compressor unloading valve

Country Status (9)

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US (1) US7874820B2 (de)
EP (1) EP1851415B1 (de)
CN (1) CN100564808C (de)
AU (1) AU2005327964A1 (de)
CA (1) CA2598206A1 (de)
ES (1) ES2588578T3 (de)
HK (1) HK1117887A1 (de)
TW (1) TW200630539A (de)
WO (1) WO2006091200A1 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20110268598A1 (en) * 2010-04-29 2011-11-03 Dan Paval Gear pump
US10746300B2 (en) 2015-04-09 2020-08-18 Bendix Commercial Vehicle Systems Llc Piston assembly for an unloader valve of an air compressor

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4431184B2 (ja) * 2008-06-13 2010-03-10 株式会社神戸製鋼所 スクリュ圧縮装置
WO2016099746A1 (en) * 2014-12-17 2016-06-23 Carrier Corporation Screw compressor with oil shutoff and method
CN113982916A (zh) * 2021-09-18 2022-01-28 江森自控空调冷冻设备(无锡)有限公司 压缩机

Citations (9)

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US1995561A (en) * 1931-11-23 1935-03-26 Belanger Joseph Conduit valve for paper pulp lines and the like
US3632231A (en) * 1970-02-19 1972-01-04 Worthington Corp Suction pressure relieving system for a rotary vane compressor
GB2119445A (en) * 1982-04-30 1983-11-16 Sullair Tech Ab Rotary positive-displacement gas-compressor
US4727725A (en) * 1985-05-20 1988-03-01 Hitachi, Ltd. Gas injection system for screw compressor
JPH02207187A (ja) * 1989-02-06 1990-08-16 Hitachi Ltd スクリュー圧縮機
JPH02248677A (ja) * 1989-03-20 1990-10-04 Daikin Ind Ltd スクリュー圧縮機の容量制御装置
JPH05157072A (ja) * 1991-12-04 1993-06-22 Ebara Corp スクリュ圧縮機の容量制御装置
JPH0979166A (ja) * 1995-09-14 1997-03-25 Hitachi Ltd 空気圧縮機
US6494699B2 (en) * 2000-08-15 2002-12-17 Thermo King Corporation Axial unloading lift valve for a compressor and method of making the same

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US4249866A (en) 1978-03-01 1981-02-10 Dunham-Bush, Inc. Control system for screw compressor
US4342199A (en) 1980-10-03 1982-08-03 Dunham-Bush, Inc. Screw compressor slide valve engine RPM tracking system
SE430710B (sv) * 1982-04-30 1983-12-05 Sullair Tech Ab Anordning for reglering av kapacitet och inre kompression i skruvkompressorer anordning for reglering av kapacitet och inre kompression i skruvkompressorer
JPH0248677A (ja) * 1988-08-11 1990-02-19 Japan Carlit Co Ltd:The 電子写真用トナー
US6302668B1 (en) 2000-08-23 2001-10-16 Fu Sheng Industrial Co., Ltd. Capacity regulating apparatus for compressors
US6881040B2 (en) * 2001-02-15 2005-04-19 Mayekawa Mfg. Co., Ltd. Multi-stage screw compressor unit accommodating high suction pressure and pressure fluctuations and method of operation thereof
US6739853B1 (en) 2002-12-05 2004-05-25 Carrier Corporation Compact control mechanism for axial motion control valves in helical screw compressors

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1995561A (en) * 1931-11-23 1935-03-26 Belanger Joseph Conduit valve for paper pulp lines and the like
US3632231A (en) * 1970-02-19 1972-01-04 Worthington Corp Suction pressure relieving system for a rotary vane compressor
GB2119445A (en) * 1982-04-30 1983-11-16 Sullair Tech Ab Rotary positive-displacement gas-compressor
US4727725A (en) * 1985-05-20 1988-03-01 Hitachi, Ltd. Gas injection system for screw compressor
JPH02207187A (ja) * 1989-02-06 1990-08-16 Hitachi Ltd スクリュー圧縮機
JPH02248677A (ja) * 1989-03-20 1990-10-04 Daikin Ind Ltd スクリュー圧縮機の容量制御装置
JPH05157072A (ja) * 1991-12-04 1993-06-22 Ebara Corp スクリュ圧縮機の容量制御装置
JPH0979166A (ja) * 1995-09-14 1997-03-25 Hitachi Ltd 空気圧縮機
US6494699B2 (en) * 2000-08-15 2002-12-17 Thermo King Corporation Axial unloading lift valve for a compressor and method of making the same

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20110268598A1 (en) * 2010-04-29 2011-11-03 Dan Paval Gear pump
US8821140B2 (en) * 2010-04-29 2014-09-02 Dan Paval Gear pump
US10746300B2 (en) 2015-04-09 2020-08-18 Bendix Commercial Vehicle Systems Llc Piston assembly for an unloader valve of an air compressor

Also Published As

Publication number Publication date
EP1851415A4 (de) 2011-07-06
CN100564808C (zh) 2009-12-02
US20090148332A1 (en) 2009-06-11
AU2005327964A1 (en) 2006-08-31
HK1117887A1 (en) 2009-01-23
EP1851415A1 (de) 2007-11-07
ES2588578T3 (es) 2016-11-03
EP1851415B1 (de) 2016-07-27
CA2598206A1 (en) 2006-08-31
CN101128647A (zh) 2008-02-20
TW200630539A (en) 2006-09-01
WO2006091200A1 (en) 2006-08-31

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Effective date: 20190125